Apparatus and method for releasing tension members for use in anchor method

ABSTRACT

Disclosed are an apparatus and method for releasing tension members for use in an anchor method, in which in state that both ends of the tension member are firmly and stably held by anchors, all or some of the wires consisting of several strands are cut, and at least one end of the cut wires is hit to release and draw the tension member. The anchor includes an anchor head having opened upper and lower ends, and being formed with a cone-shape wedge-receiving space at the upper end of the anchor head, a wedge unit seated in the wedge-receiving space of the anchor head, and having three wedges assembled together to form a first hole at the center of the wedge unit, through which the tension member is inserted, a support plate inserted into a circular groove formed at an upper portion of the first hole, and an O-shaped ring provided around three wedges so that the wedges are expanded around the support plate, a spring, positioned on an upper portion of the wedge unit, for constantly biasing the wedge unit against the wedge-receiving space of the anchor head; and the wedge cover fastened to the anchor head, with the spring being seated on the upper end of the anchor head.

TECHNICAL FIELD

The present invention relates to an apparatus and method for releasingtension members for use in an anchor method to provide soft groundreinforcement for civil engineering projects, and more particularly, toan apparatus and method for releasing tension members for use in ananchor method, in which both ends of the tension member are firmly andstably held by anchors, where all or some of the wires consisting ofseveral strands are cut, and at least one end of the cut wires is hit torelease and draw the tension member.

BACKGROUND ART

Generally, an anchor method is used to reinforce soft ground by drillinga hole into the ground, inserting an anchor member composed of agrout-feeding hose and a tension member into the drilled hole, pouringgrout into the anchor member through the grout-feeding hose, curing thegrout with the anchor member, fastening an anchor with one end of thetension member, and drawing the tension member by use of tensioningequipment to apply tension to the grout and tile ground. Such an anchormethod is mainly used for land-side protection wall construction, stonesetting works, retaining wall construction, etc.

The application of the anchor method offers advantages of increasedeffectiveness in managing downtown construction, reduction in therequired duration of works, etc. Upon carrying out further constructionin an adjacent region, drilling and boring machinery is required and theduration of works is lengthened due to the embedding of tension memberswith strength six times stronger than that of common steelreinforcements. In order to solve the above problem, an anchor forremoving the tension member after the completion of the drillingconstruction has been developed, and it is referred to as a tensionmember-releasing apparatus for use in an anchor method.

Several tension member-releasing apparatuses for use in the anchormethod have been proposed. For example, one tension member-releasingapparatus for use in an anchor method is disclosed in Korean UtilityModel Publication No. 20-0242474. In this Utility Model, the apparatusincludes a body formed with a threaded portion for fastening a cap on anouter surface of an upper end thereof and which has a wedge-receivingspace; a wedge assembly mounted in the wedge-receiving space of thebody, which has an external ring mounted on a groove formed on the outersurface of the wedge assembly for maintaining an assembled state thereofand which is radially expanded by an internal ring mounted on an innergroove, and in which a spoiler is inserted into a spoiler groove formedat a front portion of the inner groove; a locking member for seating thespoiler containing a resilient hook to the spoiler groove of the wedgeassembly; and the cap having a protrusion which is fastened to the upperportion of the body and receives a resilient hook.

According to the method for releasing the tension member by use of thetension member-releasing apparatus described above, if the tensionmember installed in the ground in a tensioning state is cut, the tensionmember is moved toward the embedded anchor by means of repulsive forceresulting from the release of the tensioning state of the tensionmember. At that time, the tension member and the wedge assembly mountedto the end of the tension member are moved into the wedges, and thus thewedges are expanded, thereby allowing the front end of the tensionmember to be released from the wedges.

The locking member assembled to the wedge assembly is also movedtogether with the tension member, and the resilient hook of the lockingmember is inserted and fixed to the protrusion of the cap. After theresilient hook of the locking member is fixed to the protrusion of thecal), all wedges of the wedge assembly are expanded to release thelocking of the tension member. Therefore, the tension member may bedrawn by pulling the tension member.

If the tension member is not released due to a weak repulsive force, thecut end of the tension member is hit by a hammer so that thetension-member is moved toward the anchor, thereby causing the resilienthook of the locking member to abut against the protrusion.

According to the conventional tension member-releasing apparatusdisclosed in the publications, if external shock is applied to the wedgeassembly with the tension assembled thereto due to carelessness,necessity or some often reason, the tension member is inserted and thusthe resilient hook of the locking member mounted on the upper end of thewedge assembly is locked by the protrusion of the cap. When this occurs,it is impossible to release the tension member from the wedge assembly.Therefore, a problem results in that the wedge assembly may not bereused because all wedges of the wedge assembly are expanded.

In addition, a significant amount of force is required to hit thetension member so that the resilient hook of the locking member isabutted against the protrusion of the cap. Also, another potentialproblem exists in that the hammer can miss the tension member fromcarelessness.

DISCLOSURE OF THE INVENTION

Therefore, an object of the present invention is to solve the problemsinvolved in the prior art, and to provide an apparatus for releasingtension members for use in an anchor method including an anchor forfirmly fastening one end of the tension member and a release fordisassembling the tension member fastened to the anchor, so that uponcarrying or working the tension member with an end mounted to theanchor, it may prevent the release of the tension member due to theexternal shock from carelessness or necessity, and the fastening orrelease of the tension member to the anchor may be repeated at severaltimes.

Another object of the present invention is to provide an apparatus forreleasing tension members for use in an anchor method, in which since asupport plate used in a wedge unit of the anchor is formed to have thecap-shaped cross section, the end of the tension member may be held morefirmly and stably.

Further another object of the present invention is to provide anapparatus for releasing tension members for use in an anchor method, inwhich all or some of the wires consisting of several strands, i.e., thetension member. which is applied with the tension by the anchorspositioned at both ends of the wire, are cut, and at least one cut wireis hit and inserted, in which the remaining wires which are not hit arerelatively pulled out from the wedge unit, and in which a diameter ofthe tension member is abruptly decreased at the moment that the wireleaves the end of the wedge unit, so that after releasing the fasteningof the tension member from the wedge unit of the anchor, the tensionmember nay be pulled out and removed.

In order to accomplish the above mentioned objects, there is provided anapparatus for releasing tension member, the apparatus including ananchor fastened to one end of a tension member, and a release mounted tothe other end of the tension member, the anchor comprising: an anchorhead having opened upper and lower ends, and being formed with acone-shape wedge-receiving space at the upper end of the anchor head; awedge unit seated in the wedge-receiving space of the anchor head andhaving three wedges assembled together to form a first hole at a centerportion of the wedge unit, through which the tension member is inserted,a support plate inserted into a circular groove formed at an upperportion of the first hole, and an O-shaped ring provided around threewedges so that the wedges are expanded around the support plate; aspring, positioned on all upper portion of the wedge unit, forconstantly biasing the wedge unit against the wedge-receiving space ofthe anchor head; and a wedge cover fastened to the anchor head, with thespring being seated on the upper end of the anchor head.

The support plate includes a support plate of a cap-shaped cross sectionto stably and firmly hold the tension member inserted into the firsthole of the wedge unit.

According to another aspect of the present invention, there is providedan apparatus for releasing tension member, including an anchor fastenedto one end of a tension member, further comprising: a release, mountedto the other end of the tension member, for fastening and releasing thetension member.

The release includes an extended pipe-type release head having a secondhole for receiving the tension member, which consists of a wire of sevenstrands laid together with a uniform pitch, the upper end of the releasehead formed with a male thread, and a release cover fastened to therelease head by engaging the male thread of the release head with afemale thread formed at a lower end of a third hole of the releasecover, in which the third hole of the release cover is provided at aninner surface thereof with a protrusion for stopping two or moreadjacent wires of the tension member.

The release is provided by assembling the release head and the releasecover, but the release head and the release cover may be integrallyformed.

According to still another aspect of the present invention, there isprovided a method for releasing tension members for use in an anchormethod, comprising the steps of: cutting at least one of wires forming atension member, which is installed with one end of the tension member ina ground together with an anchor and the other end fastened to anotheranchor, with the tension member being applied with maximum tension;hitting the entire or some of the cut wires of the tension member towardthe anchor installed in the ground to push the remaining wires from thewedge unit; repeating the hitting step, so that an outer diameter of thetension member is abruptly decreased and thus the tension member isreleased from a wedge unit, at a moment that the moved wires of thetension member leave one end of the wedge unit; and drawing the releasedtension member.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the present invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects, other features and advantages of the presentinvention will become more apparent by describing the preferredembodiment thereof with reference to the accompanying drawings, inwhich:

FIG. 1 is a cross-sectional view showing a tension member-releasingapparatus according to one preferred embodiment of the presentinvention.

FIG. 2 is an exploded perspective view of the anchor shown in FIG. 1.

FIG. 3 is an exploded view of the release shown in FIG. 1.

FIG. 4 a is a cross-sectional view depicting the state in which atension member is fixed to an anchor according to the present invention.

FIG. 4 b is a cross-sectional view depicting the process where a wedgeunit is pushed by wires of a tension member.

FIGS. 5 a to 5 c are cross-sectional views depicting the process whereinwires of tension member are pushed from a release head according to thepresent invention.

FIGS. 6 and 7 are cross-sectional views depicting an anchor according toanother embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

An apparatus for releasing tension members for use in an anchor methodaccording to the present invention will now be described with referenceto the accompanying drawings.

FIG. 1 is a cross-sectional view showing a tension member-releasingapparatus for use in the anchor method according to one preferredembodiment of the present invention, FIG. 2 is an exploded perspectiveview of the anchor shown in FIG. 1, and FIG. 3 is an exploded view ofthe release shown in FIG. 1.

As shown in the figures, the tension member-releasing apparatus for usein the anchor method includes an anchor A fastened to one end of atension member 10, which is inserted into the ground, and a release R,which is mounted to the other end of the tension member 10 and is usedfor fastening and releasing the tension member 10.

The tension member 10 includes a wire of seven strands consisting of 6strands 10 b laid together around a center strand 10 a with a uniformpitch.

The anchor A includes a wedge cover 50 used to resiliently support awedge unit 30 against an anchor head 20 by means of a spring 40. Theanchor head 20 has opened upper and lower ends, and a cone-shapewedge-receiving space 21 is formed at an upper portion of the anchorhead 20. The wedge unit 30 is seated in the wedge-receiving space 21 ofthe anchor head 20. The anchor head 20 is provided on a lower portionthereof with a plastic tube 12 such that an airtight state may bemaintained when the tension member 10 is inserted into the anchor head.The tube 12 functions as a waterproof member for preventing water frompermeating into the inside of the anchor A, thereby providing ananticorrosive effect.

The wedge unit 30 includes three wedges 31 assembled together to form afirst hole 32 at the center portion of the wedge unit through which thetension member 10 is inserted. A support plate 34 is inserted into acircular groove 33 formed at the upper portion of the first hole 32, andan O-shaped ring 35 is provided around three wedges 31 so that thewedges may be expanded around the support plate 34. An inner surface ofthe first hole 32 of the wedge unit 30 is formed with a helical orindented recess, thereby preventing the tension member 10 from slidingor leaving the wedge unit 30 when the tension member 10 is pulled.

The wedge unit 30 includes a compressive cover 42 to allow smooth motionof the respective wedges 31; a spring 40 for constantly biasing thecompressive cover 42 and the wedge unit 30 to the wedge-receiving space21 of the anchor head 20; and a wedge cover 50 fastened to the anchorhead 20 with the spring 40 located on the upper end of the anchor head20.

The reason why the wedge unit is tightened by the compressive cover 42is that the upper surface of the wedge unit 30 and the lower surface ofthe compressive cover 42 are formed to share the same inclined angle(generally, 30 degrees) in a radial outward direction, and thus thewedge unit 30 is constantly pressed toward the center. Also, the lowersurface of the compressive cover 42 may be formed to have an inclinewith an angle larger than that of the upper surface of the wedge unit 30by about 15 degrees.

The release R includes an extended pipe-type release head 60, which hasa second hole 61 for receiving the tension member 10 and which consistsof a wire of seven strands 10 a and 10 b laid together with a uniformpitch, the upper end of the release head formed with a male thread 62,and a release cover 70 fastened to the release head 60 by engaging themale thread 62 of the release head 60 with a female thread 72 formed ata lower end of a third hole 71 of the release cover, through which thetension member 10 passes. The third hole 71 of the release cover 70 islocated at the inner surface of the hole with a protrusion 73 forstopping two or more adjacent wires 10 b of the tension member 10. Alocking bolt 64 is fastened to a front end of the release head 60 toselectively lock the tension member 10.

The release head 60 and the release cover 70 are fastened to each otherby a male thread 62 and a female thread 72, but the release head 60 andthe release cover 70 may be integrally formed.

The protrusion 73 may be formed to stop one wire or two or more wiresaccording to the arrangement of the wires 10 a and 10 b.

A releasing process of the tension member will now be described indetail with reference to the tension member-releasing apparatus for theanchor method.

As shown in FIGS. 1 and 4 a; after the anchor A is fastened to one endof the tension member 10 and an anchor member consisting of the tensionmember 10 and a grout-feeding hose is inserted into a ground holedrilled by a drill, grout is poured through the grout-feeding hose andthen is cured. When the curing of the poured grout is completed, theanchor A is fastened to the other end of the tension member 10, and thetension member 10 is pulled by means of a tensioner so as to applymaximum tension to the tension member 10, in addition to the grout.

When the outwardly pulled portion of the tension member 10 is cut, thetension applied to the tension member 10 is released, and simultaneouslythe tension member 10 and the wedge unit 30 positioned at the end of thetension member are moved toward the installed anchor A against theresilience of the spring 40 by the repulsive force that is generated bycutting the tension member 10. Since the repulsive force of the tensionmember 10 is completely depleted at the time that it is equal to theresilience of the spring 40, the tension member is returned to thewedge-receiving space 21 of the anchor head 20 by the biasing force ofthe spring. At that time, the tension member 10 is maintained, as it isheld by the wedge unit 30 of the anchor A.

When the cut end of the tension member 10 is inserted into the secondhole 61 formed at the release head 60 of the release R, the end of thetension member 10 is positioned at the lower end of the protrusion 73formed at the third hole 71 of the release cover 70 through the secondhole 61 of the release head 60. At that time, the protrusion 73 formedon the inner surface of the 10 third hole 71 of the release cover 70 islaid on two adjacent wires 10 b that form the tension member 10, asshown in FIGS. 5 a and 5 b.

Then, when the end of the release cover 70 is hit by a hammer, twoadjacent wires 10 b among the wires 10 a and 10 b that form the tensionmember 10 are pulled toward the anchor A by means of the protrusion 73formed on the inner surface of the second hole 61 of the release cover70, as shown in FIG. 5 c.

The wedge unit 30 pushes the support plate 34 of the wedge unit 30against the wedge cover 50 by a distance of the two wires 10 b, as shownin FIG. 4 b, and then is returned to the original position by thebiasing force of the spring 40, as shown in FIG. 4 a.

In other words, the wedge-receiving space 21 of the anchor head 20 isoutwardly 20 expanded by an allowable range by the O-shaped ring 35provided at the outer surface of the wedge unit 30, by the pusheddistance of the wedge unit 30 when the two wires 10 b forming thetension member 10 pushes the wedge unit 30. At that time, the remainingwires 10 a and 10 b among the tension member 10, except for the twowires 10 b are pushed toward the release R hitting the tension member10.

When the external force hitting the release R is completely exhausted,the wedge unit 30 is pushed into the wedge-receiving space 21 of theanchor head 20 by the biasing force of the spring 40, such that thewedges 31 of the wedge unit 30 are radially contracted. At that time,the outer surface of the tension member 10 comes into contact with theinner surface of the wedges 31 of the wedge unit 30.

As described above, two wires 10 b among the tension member 10 areinserted into the anchor A installed in the ground by repeatedly hittingthe release R, and thus the remaining wires 10 a and 10 b among thetension member 10 that are not hit are pushed in a direction opposite tothe direction of the hit. At the moment that the relatively moved wires10 a and 10 b of the tension member 10 leave the end of the wedge 31from the support plate 34 of the wedge unit 30, the outer diameter ofthe tension member 10 is abruptly decreased. Therefore, the tensionmember 10 is released from the wedge 31 of the wedge unit 30.

Specifically, even though the wedges 31 of the wedge unit 30 arecontracted, some wires 10 b forming the tension member 10 are notfastened because they are less than the diameter of the first hole 32 ofthe wedge unit 30.

If the tension member 10 is released from the wedge unit 30 of theanchor A, the tension member 10 is applied with its one weight andslight frictional resistance only. After tightening the locking bolt 64of the release head 60, the tension member 10 is extracted and removedby pulling the release R.

The releasing method described above is carried out by cutting all oftension member 10 and drawing out the tension member 10 from the anchorA installed in the ground, but another method may be carried out bycutting only wire 10 b, or wires 10 a and 10 b, among the tension member10 and hitting at least one wire 10 b between the cut wires 10 a and 10b against a separate hand tool.

FIG. 6 depicts a support plate of a wedge unit 30 for an anchor Aaccording to another embodiment of the present invention, which issubstantially similar to the above embodiment except that a supportplate 34 a is formed in a cap-shaped cross section and has a flangearound an external lower end thereof.

In this embodiment, if the support plate 34 a is formed to have thecap-shaped cross section, the tension member 10 is upwardly pushed intothe first hole 32 of the wedge unit 30.

If the tension member 10 is deeply inserted upward, the end of thetension member 10 that is not held by the wedge 31 of the wedge unit 30is radially expanded. Therefore, the flange of the support plate 34 a isrested, thereby stably and firmly holding the tension member.

FIG. 7 is a view showing an anchor A according to another embodiment ofthe present invention, in which the support plate 34 a, which has thecap-shaped cross section assembled to an upper portion of the wedge 31of the wedge unit 30, is protruded beyond the upper end of the wedge 31.In this case, a lower end portion of a spring 40 abutted against theupper surface of the wedge 31 is formed to have a diameter smaller thanthat of an upper portion thereof, so that the spring encloses acircumference of the support plate 34 a protruded from the upper portionof the wedge 31. The embodiment does not require the compressive cover42 applied to the present invention, thereby reducing the number ofcomponents and thus decreasing the cost.

While the present invention has been described and illustrated hereinwith reference to the preferred embodiments thereof, it will be apparentto those skilled in the art that various modifications and variationscan be made therein without departing from the spirit and scope of theinvention. Thus, it is intended that the present invention covers allmodifications and variations of this invention that come within thescope of the appended claims and their equivalents.

Industrial Applicability

In the above description, when the tension member-releasing apparatusfor the anchor method according to the present invention removes thetension member installed in the ground, the process is independent fromthe problems of rust or strong repulsive force, which are common reasonsthat tension member removal fails. In addition, upon carrying or workingthe tension member that has end mounted to the anchor, the release ofthe tension member due to external shock from carelessness, necessity,etc is prevented. Moreover, the fastening or release of the tensionmember to the anchor may be repeated several times.

Since the support plate used in the wedge unit of the anchor is formedto have a cap-shaped cross section, the end of the tension member may beheld more firmly and stably. In the event that the spring's lower endhas a diameter less than that of the upper end thereof, the compressivecover is not required, thereby reducing the number of components, andthus decreasing the cost.

Furthermore, all or some of the wires consisting of several strands,i.e., the tension member to which tension is applied by the anchorspositioned at both ends of the wire, are cut, and at least one cut wireis hit and inserted. The remaining wires that are not hit are relativelypulled out from the wedge unit. The diameter of the tension member isabruptly decreased at the moment that the wire leaves the end of thewedge unit. Therefore, after releasing the fastening of the tensionmember from the wedge unit of the anchor, the tension member may bepulled out and removed.

1-10. (cancelled).
 11. An apparatus for releasing tension member, including an anchor fastened to one end of a tension member, and a release mounted to the other end of the tension member, the anchor comprising: an anchor head having opened upper and lower ends, and being formed with a cone-shape wedge-receiving space at the upper end of the anchor head; a wedge unit seated in the wedge-receiving space of the anchor head, which has three wedges assembled together to form a first hole at a center portion of the wedge unit, through which the tension member is inserted, a support plate inserted into a circular groove formed at an upper portion of the first hole, and an O-shaped ring provided around three wedges so that the wedges are expanded around the support plate; a spring, positioned on an upper portion of the wedge unit, for constantly biasing the wedge unit against the wedge-receiving space of the anchor head; and a wedge cover fastened to the anchor head, with the spring being seated on the upper end of the anchor head.
 12. The apparatus as claimed in claim 11, wherein a compressive cover for allowing smooth motion of the respective wedges is interposed between the spring and the wedge unit.
 13. The apparatus as claimed in claim 12, wherein the support plate includes a support plate of a cap-shaped cross section to stably and firmly hold the tension member inserted into the first hole of the wedge unit.
 14. The apparatus as claimed in claim 13, wherein if the support plate is protruded beyond an upper end of the wedge of the wedge unit, a lower end portion of a spring abutted against an upper surface of the wedge is formed to have a diameter smaller than that of an upper portion thereof.
 15. An apparatus for releasing tension member including a ground anchor fastened to one end of a tension member, further comprising: a release, mounted to the other end of the tension member, for fastening and releasing the tension member, after releasing tension by cutting on the other end (external ground) of tension member, which is installed with tension and fastened to the anchor.
 16. The apparatus as claimed in claim 15, wherein the release includes an extended pipe-type release head having a second hole for receiving the tension member consisting of a wire composed of several strands laid together with a uniform pitch, the upper end of the release head formed with a male thread, and a release cover fastened to the release head by engaging the male thread of the release head with a female thread formed at a lower end of a third hole of the release cover in which the third hole of the release cover is provided at an inner surface thereof with a protrusion for stopping one or more adjacent wires.
 17. The apparatus as claimed in claim 16, wherein a locking bolt is fastened to a front end of the release head to selectively lock the tension member.
 18. The apparatus as claimed in claim 16, wherein the release head and the release cover are integrally formed.
 19. A method for releasing tension members for use in an anchor method, comprising the steps of: cutting at least one of the wires and forming a tension member, in which one end of the tension member is installed in a ground together with an anchor and the other end is fastened to another anchor, with the tension member being applied with tension; hitting all or some of the cut wires of the tension member toward the anchor installed in the ground to push the remaining wires from the wedge unit; repeating the hitting step, so that an outer diameter of the tension member is abruptly decreased and thus the tension member is released from a wedge unit, at a moment that the moved wires of the tension member leaves an end of the wedge unit; and drawing the released tension member.
 20. The method as claimed in claim 19, wherein in the cutting step, all of the wires of the tension member are cut. 